Hi All
I am trying to find the gethostbyname() equivalent function in kernel space.
Does any one know that.
The reason is...
I am using UDP to transfer data from one machine to another. It is not one
time transfer. Once I get a message from machine A; I need to send some
message back to Machine A from Machine B. For that I was using the following
lines in user space program. I need to do the same in kernel space. Could
any one help me out in this.
struct hostent *data;
struct sockaddr_in server;
int sock;
sock = socket(AF_INET, SOCK_DGRAM , 0)
/* binding and all are done here */
data = gethostbyname("158.168.1.1");
memcpy (&server.sin_addrs, data->h_addr, data->h_length);
retval = sendto(sock,msg,sizeof(msg), 0, (struct sockaddr *) &server,
sizeof server);
Thanking You
Shesha
_________________________________________________________________
Cricket - World Cup 2003 http://server1.msn.co.in/msnspecials/worldcup03/
News, Views and Match Reports.
hi,
i dont think there is one similar to gethostbyname in the
kernel-space. I do think so because most of the work done by
gethostbyname is based on the nameservices and is generally not required
in the kernel-space. Implementing it should not be that big a problem.
once you have the IP of the name server (/etc/resolve.conf???) you can
always connect to it and get the IP of the given host.
Prasad.
On Mon, 24 Mar 2003, shesha bhushan wrote:
> Hi All
> I am trying to find the gethostbyname() equivalent function in kernel space.
> Does any one know that.
> The reason is...
> I am using UDP to transfer data from one machine to another. It is not one
> time transfer. Once I get a message from machine A; I need to send some
> message back to Machine A from Machine B. For that I was using the following
> lines in user space program. I need to do the same in kernel space. Could
> any one help me out in this.
>
> struct hostent *data;
> struct sockaddr_in server;
> int sock;
>
> sock = socket(AF_INET, SOCK_DGRAM , 0)
>
> /* binding and all are done here */
>
> data = gethostbyname("158.168.1.1");
> memcpy (&server.sin_addrs, data->h_addr, data->h_length);
> retval = sendto(sock,msg,sizeof(msg), 0, (struct sockaddr *) &server,
> sizeof server);
>
>
> Thanking You
> Shesha
>
> _________________________________________________________________
> Cricket - World Cup 2003 http://server1.msn.co.in/msnspecials/worldcup03/
> News, Views and Match Reports.
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
--
Failure is not an option
Hi,
Just have a look at the code at the bottom... that should make it clear.
This again is what i implemented for my project and its working fine.
> Thanks for the help. But if I am opening a socket in a lodable kernel module
> and need to send a message to a perticular IP say 158.168.1.1, then how to
> populate the structure sock_data.sin_addrs
// We dont have a inet_addr in user space.
unsigned int inet_addr(char *str)
{
int a,b,c,d;
char arr[4];
sscanf(str,"%d.%d.%d.%d",&a,&b,&c,&d);
arr[0] = a; arr[1] = b; arr[2] = c; arr[3] = d;
return *(unsigned int*)arr;
}
// Get the host...
int gethost(struct sockaddr_in *addr)
{
unsigned long ad;
addr->sin_family = AF_INET;
addr->sin_port = htons(sysctl_dos_tcpport );
ad = inet_addr("172.16.7.12");
if( ad == INADDR_NONE ){
printk("dos_select_host: Host not found");
return -EHOSTUNREACH;
}
addr->sin_addr.s_addr = ad;
return 0;
}
// Connect to the remote host...
struct socket* connect(struct sockaddr_in* sock_addr)
{
int retval;
struct socket *sock;
retval = sock_create(AF_INET,SOCK_STREAM,0,&sock);
if (retval < 0) {
printk("(connect) could not create a socket\n");
return NULL;
}
retval = sock->ops->connect(sock,
(struct sockaddr *)sock_addr,
sizeof(struct sockaddr_in),0);
if (retval < 0) {
printk("(connect) error on connect: %d\n",retval);
sock_release(sock);
return NULL;
}
return sock;
}
Hope this serves your purpose...
Prasad.
--
Failure is not an option
On Mon, Mar 24, 2003 at 10:25:11AM +0530, Prasad wrote:
>
> hi,
> i dont think there is one similar to gethostbyname in the
> kernel-space. I do think so because most of the work done by
> gethostbyname is based on the nameservices and is generally not required
> in the kernel-space. Implementing it should not be that big a problem.
> once you have the IP of the name server (/etc/resolve.conf???) you can
> always connect to it and get the IP of the given host.
Implementing it is a big problem, since gethostbyname usualy means a DNS
lookup. Best way to do it in kernel is
call_usermode_helper('/sbin/khost') and call gethostbyname in there.
> On Mon, 24 Mar 2003, shesha bhushan wrote:
>
> > Hi All
> > I am trying to find the gethostbyname() equivalent function in kernel space.
> > Does any one know that.
> > The reason is...
> > I am using UDP to transfer data from one machine to another. It is not one
> > time transfer. Once I get a message from machine A; I need to send some
> > message back to Machine A from Machine B. For that I was using the following
> > lines in user space program. I need to do the same in kernel space. Could
> > any one help me out in this.
> >
> > struct hostent *data;
> > struct sockaddr_in server;
> > int sock;
> >
> > sock = socket(AF_INET, SOCK_DGRAM , 0)
> >
> > /* binding and all are done here */
> >
> > data = gethostbyname("158.168.1.1");
However as long as you are resolving IP address, you should not ask for
gethostbyname. You should ask for inet_aton, which does exist (the name
was mentioned in some list (linux-kernel or this one) not long ago, but
I do not remember it).
> > memcpy (&server.sin_addrs, data->h_addr, data->h_length);
> > retval = sendto(sock,msg,sizeof(msg), 0, (struct sockaddr *) &server,
> > sizeof server);
> >
> >
> > Thanking You
> > Shesha
> >
> > _________________________________________________________________
> > Cricket - World Cup 2003 http://server1.msn.co.in/msnspecials/worldcup03/
> > News, Views and Match Reports.
> >
> > -
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to [email protected]
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at http://www.tux.org/lkml/
> >
>
> --
> Failure is not an option
>
> --
> Kernelnewbies: Help each other learn about the Linux kernel.
> Archive: http://mail.nl.linux.org/kernelnewbies/
> FAQ: http://kernelnewbies.org/faq/
>
-------------------------------------------------------------------------------
Jan 'Bulb' Hudec <[email protected]>
Hello!
> data = gethostbyname("158.168.1.1");
If you use gethostbyname only on numerical addresses, then it's fine to
replace it by htonl(0x98a80101) etc.
Have a nice fortnight
--
Martin `MJ' Mares <[email protected]> http://atrey.karlin.mff.cuni.cz/~mj/
Faculty of Math and Physics, Charles University, Prague, Czech Rep., Earth
A Bash poem: time for echo in canyon; do echo $echo $echo; done